The present invention relates to control systems for water treatment apparatuses, preferably but not restricted to water softeners, and more specifically to an improved brine eductor connecting a water softener brine tank to a softener control valve.
While treating hard water, as is performed in conventional water softeners, a bed of ion exchange resin or other material in a main water softener housing removes calcium and magnesium ions from the water and replaces them with sodium ions. As the hard water passes through the bed, it exchanges these hard water ions with sodium in the first soft resin it meets, creating a front or wave of ion-exchange activity called the reaction zone. As the ion exchange process continues over time, the resin bed eventually becomes ineffective for softening and must be periodically regenerated when the amount of available sodium is depleted and the ion-exchange material is saturated with calcium and magnesium. Water treatment is then suspended while the ion-exchange material is regenerated in a multi-step process to flush the calcium and magnesium ions from the resin and restore the sodium level.
A series of steps is used to replace the hard water ions with sodium ions, making the ion-exchange material active again for water conditioning. Typically, the bed is first backwashed, by reversing the flow of the incoming water, to remove sediment and loosen the bed. Next, the bed is contacted with a brine solution, whereby the ion-exchange material takes sodium ions from the high concentration brine solution and displaces the calcium and magnesium ions into the brine and out to waste. When an optimum amount of brine solution has been delivered, rinsing continues until virtually all traces of the brine solution and the unwanted hard water ions in it are discharged from the bed. After being rinsed to remove residual brine, the bed has been restored to the sodium state, known as soft resin, and is then returned to service treating hard water.
Preparation of the brine solution typically takes place in a brine tank that is kept separate from the resin tank. The brine tank, which contains a supply of salt, is filled with a measured amount of water to form a saturated salt solution. The salt supply must be replaced periodically due to depletion after repeated regenerations. During the brining or brine draw cycle of the softener control valve, brine is conventionally drawn from a remote brine tank through the softener control valve, and is directed into the resin tank. In conventional softeners, this act of drawing the brine is accomplished using a Venturi or eductor valve. Such valves are disclosed in U.S. Pat. Nos. 3,006,376; 3,538,942 and 6,644,349, all of which are incorporated by reference. Historically, eductors are an efficient way of using a venturi to discreetly mix or draw fluids from 2 to 3 different lines. As such, eductors are typically designed with a direction in mind, yet can still permit a reverse flow of fluid if provided with sufficient backflow. Such eductors are often mounted in water softener control valves, an example of which is disclosed in US Patent Publication No. 2017/0114903, incorporated by reference herein.
While conventional eductors are known to include check valves for prevention of the unwanted flow of brine back into the source or untreated water, such valves are relatively expensive and mechanically complicated. Alternate solutions to the brine draw process involve mounting external check valves, which are also considered commercially undesirable due to material and labor expense. Although there is a continuing need to prevent the flow of brine into the source water, conventional contractors prefer to obtain this preventive feature at reduced cost.
Accordingly, there is a need for an improved eductor valve with a simple but effective check valve.